Translation:If I had time, I would visit the palace.
Grammatically, it's not wrong. But "I will visit the world" makes me feel that you're outside the world and you will visit it.
For example, what do you understand from the sentence "I will visit Asia." ?
Does it mean that I am now in Asia, or I am in another continent?
That's my point of view. It may be right or wrong. :)
In Egypt, we sometimes use "Egypt" as the name of the capital "Cairo". So, In Upper Egypt for example, you can hear "I will visit Egypt", meaning "Cairo".
I don't know, if that is the same case as in Spain or not. I can't imagine how you are in Spain, and in the same time, you want to visit it, unless you want to visit other places in it. :)
Yes, in a way that's how I could use it. That doesn't mean that every time I say "Europe" I am referring to the other parts. Not at all. But in some occasions I would just say "I want to visit Europe" instead of "I want to visit the other parts of Europe which do not include Spain"
I am glad that you were able to understand me :)
Well, in one the idea that is passed is that you won't do the thing, in the other the idea is that you may do it. Let me try to explain:
using HAD If I say "If I had time, I would study history", what I'm saying is that the condition for me to study history is having time, which I currently don't, this may change in the future, but for now, I don't have time. When I use this structure I'm transmitting the idea that I don't have time to study history, so I'm not studying it.
using HAVE In the other hand, if I say "If I have time, I will study history", what I'm saying is that I may have time to study history, in which case I will, but I may not as well.
The major difference between them is that in "had" the thing is not so likely to happen as in "have". See, let's imagine a person that goes to work early in the morning and only arrives late at night, and this person says "If I had time, I would take ballet classes". It actually is possible that this person someday get to take ballet classes, but the idea she (the person) is passing when she says this is that she's not.
When it comes to "have" the probability is higher, like if someone is talking about her plans for the days and she says "I'm going to work, after I get out I'll buy grosseries and if I have time, I'll cook tomorrow's lunch". When she says this, the idea is that it is actually probable that she'll have the time to cook.
I am sorry for the huge text haha hope it helped. :)